Sound amplifier



C. C. FLYNN SOUND AMPLIFIER April 15, 1 930.

Filed May 14, 192s JNVENTOR. Ckawes C. Flynn.

ATTORNEY.

Patented Apr. 15, 1930 CHARLES G. FLYNN, OF DETROIT, MICHIGAN scum)mamma Application med May 14,

My invention relates to a new and useful improvement in a soundamplifier or sounding chamber used on various articles such as loudspeakers for radios, phonographs, and

so forth.

It is an object of the invention to provide a sound amplifying device ofthis class in which the sound led thereinto will be deflected anddirected at opposite sides of the entry into a plurality of soundconducting cham-V bers so that at op osite sides of the entry thereshall be provided a plurality of sound outlets.

lt is another object of the invention to provide reecting and dedectingsurfaces in these sound conducting chambers co-ordinated with eachotherso that as the sound issues from the various sound conducting chambers aharmonious blending of these sounds will result, accomplishing the4amplifying desired and effecting an increasing'in volume anda mollifyingofthe tone so that a mellow, soft and smooth tone may result from theuse of the amplifying device.

It is another object of the invention to provide a sound amplifyingdevice in which a plurality of sound conducting chambers are so arrangedand co-ordinated that a wide range of sound may be clearly andin amaterial manner transmitted therefrom thus affording 'an amplifyingdevice in which the lower notes of the scale and the high notes will beequally distinct.

Dther objects will appear hereinafter.

The invention consists inthe combination and arrangement of partshereinafter described and claimed.

'The invention (will be best understood by a reference to theaccompanying drawings which form a part of this specification and inwhich,

Fig. 1 is a central longitudinal horizontal sectional view of theinvention with parts broken away.

Fig. 2 is a sectional view taken on line 2-.2

of Fig. l. p

Fig. 3 is a secional view taken on line 3-3 of Fig. 4:.

Fig. 4:, is a fragmentary sectionall view taken on line li-Jl of Fig. 1.

1928. Serial No. 237,467.

lnsound amplifying devices such as those of the folded horn type, thegenerally accepted theory of design is based on rate of increase in areain values of an exponential equation or combinations ofV exponentialcurves and straight lines to-allow for rates of expansion along thesepredetermined lines. For sound amplifying devices basedon the theory ofsound vibration lbeing in line with the direction of propagation, thedesign may be such .G0 that thel sound passages increase in width alongdimensions which are plotted as harmonic means between the initial andnal openings as distinguished from harmonic sound passages. G5

In the present invention the rate of increase in width is along thecontinuous curve from the initial to the inal opening. In this foldedtype, the first section is initially a complete individual horn withwidth increasing as harmonic means between the initial and finalopening. This section then opens into another section having for itsinitial opening the outlet opening of the first section and its widthprogressing from the inlet to the outlet increases in width as harmonicmeans so that there is virtually provided one horn opening into another.

ln types of` sound amplifiers now in use, the amplifying of both highand low frequencies occur. in the same space and the higher harmonics orchords are lost or smothered b-y interference.' By having one sectionopening into a pair ofdouble sections, one of a smaller rate of increaseof area than the other, te handle the notes of higher frequencies ofvibration and the other to take care of notes of lower frequencies ofvibration, the interference of the harmonics of higher pitch with theharmonics of lower pitch is reduced toa minimum. 4

l A further reduction of this interference is edected by providing inthe larger section a greater space of travel for the sound waves ofnotes of lower pitch so that the time of travel from the inlet to theoutlet inthe amplifying device is variedin the different passagesrovided. This also results in a blending o the sounds which produces themellow mollied effect. The four separate outlet openings of 10@ theamplifier also produces the effect of solidity or depth or of spacewhich cannot be obtained when a single outlet is used. l

The sound amplifier 4illustrated to accomplish these results comprisesside walls 7 and 8 which m'ay be made of wood or other suitablematerial, preferably resonant. Mounted on the inner surface of the walls7 and 8 at opposite positions are supporting plates 9 and 10. Extendingbetween 'the plates 7 and 8 atthe lower edge and at opposite endsthereof are connecting blocks 11 and 12 which are secured at theiropposite ends to the walls 7 and 8. Engaging the edges of the walls 7and 8 and the upper surface of the blocks 11 and 12 is a cover 13preferably made from light material such as parchment and the like.Formed in the cover 13 preferably centrally thereof ois an opening 14extended through which is a collar 15 connected by a screw 16 to passageforming walls 17 and 18. Secured by these passage forming walls 17 and18at the upper ends thereof are wedges 19 and 20 which extend as shown inFig. 1 inwardly of the housin formed by the cover 13 and the side wallsg and 8 beyond the upper edge of the securing plates 9 and 10. As shownin Fig. 1 the outer faces of these wedge members 19 and 20 lie in planesparallel to each other.

Secured to and engaging at their opposite ends the plates 9 andlO areblocks 21 and 22, the upper edge of these blocks 21 and 22 extendingslightly above the lower edges of the wedges 19 and 20. The inner facesof these blocks 21 and 22 are planar surfaces which l engage the edgesof the passage forming members 17 and' 18 and extend downwardly belowthe lower ends thereof. Projecting between and connected to at oppositeends the plates 9 and 10 at, the lower edges thereof is a reflectingblock 23 which is spaced as shown in Fig. 3 and Fig. 1 below the loweredges of the passage forming members 17 and 18, the outer face of theblock 23 lying flush with the lower ends of the blocks 21 and 22 and thelower edges of the plates 9 and 10. The upper surface of the block 23 isprovided with recesses 24 and 25 which are curved from the point 26which lies in the longitudinal axis of'the'passage formed by the members17 and 18 and the wedges 19 and 20.

Engaging the surfaces of the plates 9 and 10 is a cover 27' formed fromlight material such as wood, parchment,and the like. Re- Ataining blocks28 and 29 engage the outer surface ofthe cover 27 at its lower edge andserve to reinforce the `housing, the ends of the members 28 and 29 beingsecured at the side walls 7 and 8. A screen 30 is mounted 0n the forwardor open side of the housing.

In operation, the sound waves entering the housing through the collar 15will pass downwardly between the passage Iforming members 17 and 18 andoutwardly at the ends thereof being deflected by the recesses 24 and 25thence upwardly in the passages 31 and 32, these passages progressing incross sectional area from the inlet to the outlet end. The Sound whenreaching'the outlet end of the passages 31 and 32 is-free to pass overthe upper edges of the blocks 21 and 22 and outwardly in the passages 33and 34. It is also free to pass between the edves of the cover formingmembers 27 and 2 outwardly in the assages 35 and 36.

T ese passages 33 and 34 also progress in cross sectional area,increasing in size from the inlet end to the outlet end, ,the inletendin cross sectional area being equal to the outlet end of the passages 31and 32 in cross sectional area. The passages 35 and 36 also increase incross sectional area from the inlet end to the 'outlet end and thisincrease in cross sectional area is on a predetermined ratio, theincrease being along dimensions which may be plotted as harmonic means.In this way the passages outlined herein are produced in a practicalworking device. Experience has shown that the notes of higher pitch willordinarily be transmitted outwardly through the passages 33 and 34 andthat the notes of lower pitch or of greater wave length will betransmitted outwardly through the passages 35 and 36. The dierence inlength of these passages is evident from Fig. 1 and this difference inlength compensates for the difference in the length of the sound wavesand elfects a harmonious blending of the sounds issuing from the outletends of the passages 33, 34, 35, and 36.

' While I have illustrated and described the preferred form of myinvention, I do not wish to limit myself to the precise details ofstructure shown, but desire to avail myself of such variations andmodifications as may comewithin the scope of the appended claims. Havingthus described my invention what I claim as new andydesire to secure byLetters Patent is: l

1. A sound amplifier of the class described, comprising: a housinghaving side walls sup-v porting plates mounted on said side walls; acovering for said side walls; a sound passage extending inwardly of saidhousing, projecting beyond said supporting plates; a pair of coverings,each positioned on said supporting plates at opposite sides of saidpassage, said supportin plates cooperating with said sound passage ordividing said housing into a plurality of pairs of outlet passages. 2. Asound ampler of the class described, comprisin a housing having sidewalls; a covering` or said housing; a sound passage projecting inwardlyof said housing; supporting plates mounted on the inner surface of eachof said side walls projecting laterally pairs of sound conduits .incommunication with each other and in communication with said soundpassage.

3L A device of the class described, compris- 5 ing: a housing havingside walls; a covering for said side walls; a sound passage projectinginwardly yof said housing; supportin plates mounted on the inner surfaceof sai side walls; partition plates engaging at opposite ends saidsupporting plates and at their facessaid sound passage; a pair ofcoverings, each engaging the edges of said supporting plates at oppositesides of said sound passage; cross hars engaging said side walls and theouter surface of said pairs of coverings adjacent the lower edgethereof.

4. A device of the class described, comprising: a housing having sidewalls; a covering for said side walls; a sound passage projectinginwardly of said housing; supporting plates mounted on the inner surfaceof said side walls; partition plates engaging at opposite ends saidsupporting plates and at their faces said sound passage; a pair ofcoverings,

each engaging the edges of said supporting plates at opposite sides ofsaid sound passage; cross ars engaging said side walls and the outersurface of said pairs of coverings adjacent the lower edge thereof; anda sound reflecting block engaging said supporting plates adjacent thelower edge thereof at the end of said sound passage, said sound pas-`sage communicating around its sides and between said pairs of coveringswith a plurality of sets of outlet passages.

In testimony whereof I have signed the foregoing specification.

' CHARLES C. FLYNN.

